查找在相同扫描会话中获取的两个MR数据集的相同切片位置的坐标(mm) [英] Finding the coordinates (mm) of identical slice locations for two MR datasets acquired in the same scanning session

问题描述

我有两个MR采集，第一个是3D采集(1x1x1 mm3)，第二个是2D采集(2.24 x 2.24 x 5.00 mm，轴向切片).高分辨率数据集是全头3D采集，如果在轴向方向上被切片，则将给出176个切片(方向最初在采集中是下垂的). 2D采集仅包含3个轴向切片，这些切片被选为靶向大脑中的特定区域并被连续采集.

是否有可能知道3D高分辨率数据集中的哪个切片与2D数据集中的3个切片准确对应，假设对象没有在两次扫描之间移动并且这些数据集是在同一扫描会话中获取的? 我正在针对这两个数据集寻找dicoms，并尝试使用ImageOrientationPatient和ImagePositionPatient标签来尝试准确地找出2D扫描中的切片相对于磁体的等角点的坐标.这样，我就可以知道2D采集中第一个切片相对于磁体的等角点的确切坐标，并假设两次扫描共享相同的原点，那么我可以确切地知道3D扫描中哪个轴向切片对应于坐标? 我面临的问题是，两次采集的ImageOrientationPatient向量是不同的，因为高分辨率是通过矢状方向规范指定的(尽管3d并可以在任何方向上获得切片)，而2D数据是作为轴向切片专门获得的.

具有dicom处理经验的人是否可以对我如何链接两次扫描提供一些启发?由于这是一次相同的扫描会话，因此我假设这两次采集的参考位置应该相同.正确吗?

解决方案

ImagePositionPatient仅在一次扫描中获取所有图像时才可靠地引用相同的坐标系.不幸的是，没有对患者进行校准"可以确保特定坐标始终引用同一患者中的相同位置.

假设您的扫描情况就是如此，则任务非常简单.每次扫描的完整几何形状定义为:

• ImagePositionPatient(0020,0032)-每个切片左上像素的坐标

• ImageOrientationPatient(0020,0037)-每个切片的方向矢量，即像素行和列与之对齐的轴

• PixelSpacing(0028,0030)-每个像素的高度和宽度(是，y维度在这里先！)

现在，您已经准确地知道了两次扫描中每个切片的每个像素的位置，剩下的任务是在3D扫描的维度上表示2D扫描的左上像素.我会使用坐标变换来做到这一点，但是其他方法也可以工作.

I have two MR acquisitions where the first one is a 3D acquisition (1x1x1 mm3) and the second is a 2D acquisition (2.24 x 2.24 x 5.00 mm, axial slices). The high resolution dataset is a full head 3D acquisition that gives 176 slices if resliced in the axial direction (orientation was initially saggital in the acquisition). The 2D acquisition only contains 3 axial slices that were selected to target specific regions in the brain and were acquired continuously.

Is it possible to know, which slices in the 3D high resolution dataset correspond accurately to the 3 slices in the 2D dataset assuming the subject did not move in between scans and that these datasets were acquired in the same scanning session? I am looking at dicoms for these two datasets and trying to use the ImageOrientationPatient and ImagePositionPatient tags to try and find out accurately what the coordinates of the slices in the 2D scan would be with respect to the magnet's isocenter. That way I can tell the exact coordinates of the first slice in 2D acquisition with respect to the magnet's isocenter and assuming the two scans share the same origin, I can then know exactly which axial slice in 3D scan the coordinates correspond to? The problem i am facing is that the ImageOrientationPatient vectors are different for both the acquisitions since the highres was acquire with the sagittal orientation specificiation (though 3d and can obtain slices in any direction) whereas the 2D data was acquired specifically as axial slices.

Could someone who has experience with dicom handling kindly throw some light on how I can link the two scans? Since it was the same scanning session I am assuming the reference position for these two acquisitions should be identical. Is that correct?

解决方案

ImagePositionPatient is reliably referencing identical coordinate systems only when all images were taken in one scan. Unfortunately there is no "calibration to the patient" which ensures that a particular coordinate always references the same position in the same patient.

Assuming this is the case in your scan, the task is pretty simple. The full geometry of each scan is defined by:

• ImagePositionPatient (0020,0032) - the coordinate of the top left pixel of each slice

• ImageOrientationPatient (0020,0037) - the orientation vectors of each slice, i.e. the axes to which the pixel rows and columns are aligned to

• PixelSpacing (0028,0030) - the height and width (yes, the y-dimension comes first here!) of each pixel

Now that you precisely know the position of each pixel of each slice in both scans, the remaining task is to express the top left pixels of the 2D scan in the dimensions of the 3D scan. I would use coordinate transformation to do that, but other methods would work as well.

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